to be insufficient to raise the weight of their bodies to the height of the mountain, and hence they conclude that the lacking energy at least must have been derived from non-nitrogenous materials.
Their experiments were well designed for the purpose intended, and the criticisms of Professor Flint (pp. 40–43) that the decrease in the excretion of nitrogen during and immediately after the work was due to the abstinence from albuminoid food, and that no comparison of rest with work was made, while doubtless well founded, do not touch the point at issue, viz., that a certain amount of work was performed and a certain amount of proteine destroyed, and that the latter was not, according to their calculations, sufficient to yield the amount of force actually exerted. The only grounds upon which the validity of their results can be successfully disputed are either that the principle of calculation employed by them or their data as to the heat of combustion of proteine were erroneous. We shall return to this point later. It may be added, in regard to the experiments of Voit and the other investigators in this field, that they are free from the failings which Professor Flint finds in those of Fick and Wislicenus, and also of Parkes.
The experiments of Dr. Parkes, which Professor Flint apparently regards as at least partially sustaining the view which he advocates, show in the great majority of cases either no increase or a slight decrease of the excretion of nitrogen as a consequence of work, and Dr. Parkes himself expressly says ("Journal of the Royal Society," vol. xix., p. 349): "The result of both series was, so far, to confirm the experiments, which show that the changes in the nitrogen of the urine. . . are small in extent, and afford no measure of the work."
Professor Flint's chief reliance, however, seems to be the experiments made in 1876 by Dr. Pavy, and published in a series of papers in "The Lancet," and his own experiments made in 1870 ("New York Medical Journal," June, 1871).
These two series of experiments differ decidedly, both in method and results, from those heretofore mentioned, both of them showing, according to their authors, an increased elimination of nitrogen through the kidneys as a result of muscular exertion. They were made upon two pedestrians, Perkins and Weston, during the performance of various feats of pedestrianism, and hence under conditions that excluded an exact measurement of the amount of work performed. Unfortunately, also, they could not, from the nature of the case, be made with that rigorous control of all the conditions of experiment which is essential in such researches; and they suffer under various sources of inaccuracy which materially lessen their value.
In the first place, no attempt was made to regulate the diet of the two men; they ate what and when they chose. In most experiments on this subject it has been considered necessary to employ a perfectly uniform diet as regards nitrogen, and an instructive example of the pains taken to insure it may be found in a paper by Voit and Petten-
